A fuel cell is a device for changing chemical energy into electric energy. In a general fuel cell, a gas phase fuel such as hydrogen is supplied to an anode (electrode for oxidation), and an oxidizer such as oxygen is supplied to a cathode (electrode for reduction). Once the fuel is oxidized in the anode, electrons are discharged from the fuel to an external circuit connected to the anode and the cathode. In the cathode, the oxidizer is reduced by using the electrons provided by the oxidized fuel.
In a hydrogen/oxygen fuel cell, hydrogen is supplied to an anode, and oxygen is supplied to a cathode. The hydrogen is oxidized to form hydrogen ions and simultaneously discharge electrons to an external circuit. The hydrogen ions move to the cathode through a conductive polymer film to react with the oxygen species thereby forming water. A typical reaction of a hydrogen/oxygen fuel cell is as follows:Anode: 2H2→4H++4e−  (1)Cathode: O2+4H++4e−→2H2O (acidic) O2+2H2O+4e−→4OH− (alkaline)   (2)Net reaction: 2H2+O2→2H2O   (3)
In order to cause the oxidation reaction and the reduction reaction in the fuel cell at a rapid reaction rate and a low overpotential, an electrocatalyst is required. Where no eletrocatalyst exists, a general electrode reaction occurs in a very high potential state. The eletrodecatalyst increases the electrochemical reaction rate, and thus, can operate the fuel cell at a low potential.
Meanwhile, since platinum has a high catalyst property, platinum and a platinum alloy material are generally used as electrocatalysts for an anode and a cathode of a fuel cell. However, platinum is disadvantageous because it is highly expensive and increases the preparation costs for the fuel cell.
Accordingly, development of a low-priced electrocatalyst, which has the same catalyst property as that of platinum or an improved catalyst property over that of platinum, has been demanded.
The present disclosure provides an electrocatalyst, which improves efficiency of an oxygen reduction reaction (ORR) in a fuel cell and contains no platinum. Specifically, the present disclosure provides an electrocatalyst for oxygen reduction including a silver/silver halide composite, a fuel cell including the electrocatalyst for oxygen reduction, and a method for preparing the electrocatalyst for oxygen reduction.
However, the objectives sought to be achieved by the present disclosure are not limited to those described above. Other objectives, which are sought to be achieved by the present disclosure but are not described herein, can be clearly understood by one of ordinary skill in the art from the descriptions below.